^ You have a bigger tank then 55gal? Those frontosas are going to need a bigger tank when they get bigger, even for 2 that is too small.
I agree with Mike's advice. Overstocking isn't bad but dont go overboard. Stick to a few species that you really like and get a good male to female ratio b/c that will also help with agression (the more females per male the better). The rockwork will also help break down territories and allow hiding areas. I had 8 or so of mixed mbuna in my 55gal when I had it running and it was fine to me when they were all grown at 6 inch size. You can do a little more then that, but I wouldn't go crazy.
